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Author: search.filters.author.Kittiwongwattana, ChokchaiSubject: search.filters.subject.Colletotrichum fructicola

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    Biocontrol Potential, Genome and Nonribosomal Peptide Synthetase Gene Expression of Bacillus velezensis 2211
    (2023-01-01)
    Niemhom, Nantawan
    ;
    Kittiwongwattana, Chokchai
    Members of the genus Bacillus produced a diverse group of antimicrobial compounds. Here, we presented the antifungal activity and genome sequence analysis of Bacillus sp. 2211, a potential plant-growth-promoting bacterium. Bacterial supernatants from strain 2211 cultures in nutrient broth (NB) and potato dextrose broth (PDB) suppressed the mycelial growth of Pyricularia oryzae, Colletotrichum aenigma, Colletotrichum fructicola and Fusarium oxysporum. The supernatants were also able to suppress spore germination of these fungi, except for F. oxysporum. However, the supernatant from PDB displayed a significantly higher inhibition activity than NB. Additionally, the supernatant from PDB significantly reduced the disease severity caused by P. oryzae on rice seedlings. The genome of strain 2211 was sequenced. The highest digital DNA-DNA hybridization (80.1%) and average nucleotide identity (97.57%) levels indicated that strain 2211 was a member of the species Bacillus velezensis. The phylogenomic analysis showed that it clustered with B. velezensis NRRL B-41580<sup>T</sup>, B. velezensis KACC 13105 and B. velezensis subsp. plantarum FZB42<sup>T</sup>. The gene expression analysis showed the up-regulation of nonribosomal peptide synthetase (NRPS) genes bmyA, fenB and dhbE in PDB, compared to NB. This work demonstrated that the culture media affected the antagonistic activity of strain 2211 possibly through the modification of NRPS biosynthesis genes.
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    Correlation of Antifungal Activities and Nonribosomal Peptide Synthetase Gene Expression of Bacillus siamensis 1021
    (2022-03-01)
    Nuwong, Warinya
    ;
    Kittiwongwattana, Chokchai
    Members of the genus Bacillus were biocontrol agents against various phytopathogenic fungi. Several factors affected the regulation and production of nonribosomal peptides (NRPs) in Bacillus species. The aim of this study was to examine how culture media influenced the antagonistic activities and gene expression of Bacillus siamensis 1021. The bacterial supernatant from potato dextrose broth (PDB) exhibited higher inhibitory effects against mycelia of Pyricularia oryzae and Colletotrichum fructicola, when compared with those from nutrient broth (NB) and minimal salt medium (MSM). However, the biocontrol activities of these supernatants were not significantly different when they were tested against P. oryzae and C. fructicola conidia. Additionally, the bacterial supernatant from PDB significantly reduced the disease severity caused by P. oryzae in rice seedlings when compared with the water-treated control group. The genome of strain 1021 was sequenced, and biosynthetic gene clusters of nonribosomal peptides surfactin, fengycin and bacillibactin were identified. Effects of PDB, NB and MSM media on expression levels of core biosynthetic genes of surfactin (srfAA), fengycin (fenC) and bacillibactin (dhbE) gene clusters were determined by reverse-transcription quantitative PCR. fenC expression was significantly increased in PDB and corresponded with the antagonistic activities against fungal mycelia. Conversely, expression of the regulatory genes comA and codY in PDB were highly reduced in PDB, indicating their negative relation with fenC expression. This expression analysis indirectly suggested that fengycin was potentially the bioactive compound of B. siamensis 1021 against P. oryzae and C. fructicola.